U.S. Pat. No. 4,877,588 discloses an ozone generating apparatus based on the well known and widely used corona discharge method for converting oxygen and air to ozone. The patent offers improvements to the technology by providing a construction with improved cooling efficiency which, in turn, benefits the electrical efficiency as well. The cell achieves this by alternating corona regions with corona-free regions in the airflow path, and using both the air itself and an external cooling medium to achieve the cooling. The corona discharge occurs in an annular space of narrow width, cooled from both sides. The corona discharge occurs in bands spaced along the length of the annular passage, with heat exchange occurring in the intervening corona-free regions.
A key factor in the corona discharge is the width of the annular passage (i.e., the radial distance between the two cylindrical walls which form the boundaries of the annulus) in which the corona discharge takes place. This width generally ranges from about 1 mm to about 3 mm, and is generally specified to tenths of a millimeter. A variation in the gap width, such as might result from impact or injury to the cell, or from expansion or contraction of the cell materials, may be detrimental to the cell performance. A gap which is too small may cause arcing or short-circuiting, and one which is too large may destroy the ability of the cell to produce a corona discharge. In either case, there is a loss or waste of power and a decrease in the efficiency of the conversion of oxygen to ozone.
An improvement in the ozone cell of U.S. Pat. No. 4,877,588 is presented herein. In accordance with this improvement, the cylinder forming the heat exchange wall between the passage in which the corona discharge takes place and the outer cooling annulus is divided into sections alternating between rigid and deformable. The rigid sections extend along the corona discharge regions, and the deformable sections extend along the corona-free regions. The deformable sections have corrugated contours which provide them with a bellows effect which give the sections flexibility, and in addition, they improve the cooling efficiency by both increasing the heat exchange area and promoting turbulent rather than laminar flow. The deformable sections are thus free to accommodate any expansions or contractions of either themselves or adjacent sections, lessening the strain on the rigid sections to be maintained at a selected gap width from the inner cylinder, controlling the annular corona discharge space to a close tolerance. Spacers are placed at locations adjacent to the rigid sections to maintain the critical spacing between the cylinders.
The advantages offered by this improved construction are many and varied. As mentioned above, the deformable sections permit the materials of construction of the cell to respond to temperature changes occurring in the cell by expanding and contracting, while still maintaining the critical spacing in the corona discharge regions. This provides better control over the corona discharge and, consequently, over the rate and efficiency of ozone generation and use of electricity. The bellows structure in the deformable sections permits the intermediate cylinder to bend from its axis, as well as to expand and contract longitudinally along the axis. Still further, the corrugated contour of these deformable sections imparts turbulence to the flow of fluid on both sides, improving heat exchange and mixing. Thus, both the ozone-containing air and the external heat exchange medium (generally, water) experience turbulent flow, improving the heat exchange efficiency, and consequently either lowering the power requirement for a given production level or increasing the production obtained at a given power level.
Other advantages and features of the invention will be apparent from the description which follows.